1. Field of the Invention
The invention relates to the field of pacemaker leads and catheters and methods for insertion of the same, and in particular to leads used in veins such as in connection with pacemaker procedures such as pacemaker lead insertion.
2. Description of the Prior Art
There are many medical procedures which require a puncture and catheterization of an artery or vein for various purposes.
In the prior art process of percutaneous puncture, a guidewire is introduced into the vessel through a hollow needle. The needle is withdrawn leaving the guidewire in the vessel. A TEFLON dilator and venous sheath assembly are then advanced in a rotary motion over the guidewire into the vessel. The TEFLON dilator and the guidewire are then removed leaving the flexible sheath in the vessel. At this point, various types of catheters or leads are inserted using the sheath as a conduit to avoid tearing or further trauma to the vessel wall.
In the case where a pacemaker lead must be permanently inserted into the patient, the pacemaker is subcutaneously implanted in the patient and the lead, which extends from the pacemaker into the heart chamber, remains permanently disposed through the vessel wall and in the vessel lumen. A sheath is nevertheless used in order to guide insertion of the lead into vein lumen, but must be removed leaving the lead in place. However, the sheath cannot simply, in all cases, be slipped over the the exterior end of the pacemaker lead which may be provided with a special termination for connection to the pacemaker.
In this case, the prior art has devised a number of splittable or peel away sheaths. The sheath is scored so that it is withdrawn by splitting or peeling it off from the pacemaker catheter. See Phillip O. Littleford, et al, "The American Journal of Cardiology," Vol. 43,pp.980-982 (May 1979); Littleford, "Apparatus and Method for Inserting an Electrode," U.S. Pat. No. 4,166,469 (1979); Littleford, "Method for Inserting Pacemaker Electrodes and the Like," U.S. Pat. No. 4,243,050 (1981) and Littleford, "Split Sleeve Introducers for Pacemaker Electrodes and the Like," U.S. Pat. No. 4,345,606 (1982); Osborne, "Tear Apart Cannula," U.S. Pat. No. Re. 31,855 (1985), a reissue of U.S. Pat. No. 4,306,562 (1981); Boarini et al., "Peelable Catheter with Securing Ring and Suture Sleeve," U.S. Pat. No. 4,411,654 (1983); Moorehead, "Medical Layered Peel Away Sheath and Methods," U.S. Pat. No. 4,983,168 (1991). A splittable cannula is also taught by Kousai et al., "Medical Tool Introduction Cannula and Method of Manufacturing the Same," U.S. Pat. No. 4,883,468 (1989).
However, in each of these prior art sheath assemblies, once the sheath has been inserted the sheath provides a passage for the free flow of blood. In practice a significant amount of bleeding may occur at the operation site, which requires constant mopping and cleaning. The amount of loss of blood during an operation may begin to have a negative impact upon the patient.
Secondly, in addition to the sheath assembly providing an open passage for the loss of blood, the sheath assembly also provides an open passage for the introduction of air into the vein. The inadvertent introduction of air into the blood system causes air embolism in the patient and its consequent negative effects.
Thirdly, clotting may be formed in the lumen of the sheath if the sheath remains in for a prolonged time, and this may cause embolism to the lung and its consequent negative effects.
Because of the three problems above, the prior art splittable sheath has to be removed as soon as the lead is introduced into the vessel lumen, although it is very desirable to retain the sheath in place throughout operation because the lead can be manipulated much easier without interference from other existing lead or tissue friction and can be exchanged freely without repeated sheath insertion trauma.
When the catheter or lead is introduced in the sheath, a certain amount of blood leakage will occur between the catheter and the sheath walls. The prior art has also devised hemostatic valves which provide a seal around the catheter introduced through the sheath. One such sheath and hemostatic valve is manufactured and marketed by Cordis Corp. of Miami, Fla. as the UNISTASIS valve in the Cordis catheter sheath introducer. Another example is manufactured by Bard of Billerica, Mass. as the 5F HEMAQUET introducer. A hemostatic valve combined with a splittable sheath is also illustrated in Schiff, "Introducer Assembly for Intra-Aortic Balloons and the Like Incorporating a Sliding, Blood-Tight Seal," U.S. Pat. No. 4,473,067 (1984).
However, all the prior art hemostatic valve structures, even when combined with a splittable sheath, such as shown by Schiff, are integral or or rigid units, which do not split and must be removed by sliding along the end of the catheter. In the case of Schiff, the sheath is split in order to appropriately position the balloon catheter. However, after the baloon angioplasty procedure is completed, the entire catheter is removed so that at no point is the hemostatic valve entirely removed from the catheter nor need it be.
What is needed then is some type of sheath and valve system which can be used in connection with our vessel introducers, which introducers can then remain in place without risking undue bleeding, air embolism, or clotting while retaining the advantages of an introducer sheath for free lead exchange and easier lead manipulation.